Colloidal graphite suspensions



June 23, 1936. o. A. G. VON MANDELSLOH 2O45501 COLLOIDAL GRAPHITE SUSPENSIONS Filed' Dec.- 21, 1933 OTTO ALBRECHT GRAF VON MANDELSLOH V AI'ITORNEYS Paientecl June 23, 193 6 PATENT OFFICE 2045501 COLLOIDAL GRAPHI'IE SUSPENSIONS Otto Albrecht Graf Gennany, assignor to brik Florsheim vorm. tiengesellschaft, Flors many Application December 21,

von Mandelsloh, Dresden,

the firm Chemische Fa- Dr. H. Noerdlinger Akheim-on-the-Main, Ger- 1933, Serlal N0. 703,486

In Germany December 29, 1932 2 Claims.

As is known graphite finds many applications in the lubrieant art. Now whilst graphite ls suitable as it stands for rough lubricationi. e. for

example for the lubrlcation of vehicles or the 5 like-various difficulties occur in the case of its employment for fine lubrication. Methods are already known by means of which the graphite is chemically suspended in mineral oil. These known methods for the production of colloidal graphite suspensions are, howeverrather expensive; theyrequire .a large plant and in this case a considerable loss of graphite is unavoidable.

The present invention relates to a method for obtaining colloidal graphite suspensions mechanic.ally. Now whllst it ls not possible to obtain colloidal graphite suspnsions with colloid mllls or ordinary multiple-roller mills, it has been found that the production of colloidal graphite suspenslons is efiected when accrding to the invention the graphite mixed with a liquid bindlrig agent, preferably a thinly fluid mineral oil, 1:0 form a paste is triturated under extremely high pressure in single-roller and multiple-roller mills, triturating mills, and llke mills withsurface trlturation.

For normal trituration of pigments or the like in oils, Iats, or the llke such a high pressure cannot be employed because if it were the rollers would immediately run bot. It is only owlng" to the fact that the graphite to be trlturated acts a'o the same time according to the invention as a. valuble lubricant that lt is posslble to employ a specially high pressure.

For carrying out the present method there ma.y be used for example a so-called single-roller mll1. As is known, slngle-roller mills ha.ve a, single triturating roller, over whic for produclng a tritura.tion over as large a, surface as possible, a trit urating bar of a width of several centimetres 1s moved to am]. fro. Such slngle-roller mills are very sensitive as regards the pressure of the triturating bar on the trituratlng roller. In the case of thin material to be trlturated that is poor in fat-there occurs a1; the slightest over-pressure a grinding of the triturating bar on the triturating roller so that the machinle is immediately brought to rest and the roller is badly injured. Even in the case cf the employment of masses that are rich in fat the pressure cf the triturating bar on the trituratlng roller is limited beeause when the pressure is great the triturating bar presses the lubricant away from the roller so that the disadvantages herelnbefore mentioned arise.

In the case of the employment of graphite suspensions these phenomena do not occur. The triturating bar can be pressed upon the triturating roller with the greatest pressure that can be technically exerted, and whereas in the case oi previous single-roller mills the highest pressure that can be employed ls 150 to 200 grammes per square millimetre, according to the invention in the case of the trituratlon cf graphite suspensions the pressure may be ralsed to 1.5 to 2.0 kllo grammes per square millimetrel. e. to about ten times the amount. Only in the case of the .employment of this pressure are the gr.aphite p2.rticles especially when the graphite paste ls passed repeatedly through the machine eontinually more and more crushedand assume in t he course of the grinding or triturating process the desired colloidal condition.

Multiple-roller mills may also be used for the production of colloidal graphite suspensions according to the inventlon; but in that case the following points must be observed.

In the case of ordinary roller mil ls wlth several rollers there occurs only a linear trlturation of the materlal to be ground, which is not sufllcient for the colloidal comminution of the graphite. When a large over-pressure is i1sed in the case of these multiple-roller mills, there occurs a breaking of the rollers, which, even 113 hardly measurable, destroys their linear contact and consequently their aCtion.

Now it has been found that even in the case of multiple-roller mills, which otherwise allow only a, linear trituratlon, under high pressure is rendered possible by providing the several rollers with an excessively crowned or longitudinally outwardly cu1ved surface. Ordinarily the curvature or spherlcal p'olishlng, which is measured with optical instruments, amounts 1:0 /L. Accordiing to the invention the curvature or spherical pollshing of the rollers is increased 110 five times-i. e. 1:0 50l.

The excessive spherical polishing of the triturating rollers enables the necessary pressure to be applled in such a. manner that instead of.the trituration occurring as otherwise in ordlnary multiple-rollermills only linearly, which is not suflicient foracolloidal comminutionof i;he graphite even when the strongest pressure is employed, there occurs a. much more effectual surt ace trituration. The surfaces of contact between the several rollers are in consequence 013 the high pressure and of the exaggeratedly curved surface no longer linear but spindle shaped, 'corresponding to the cross-sectlon of a bl-convex lens. In the case of roller mllls with several rollers lt is advisable also td glve indivldual rollers a. considerably higher rotational velocity than the other a surface trituratlon rollers, so that the rollers not only act on the material 1:0 be ground coming between them so as to crush it but also exert a rubbing action. v

The varlation 01 the rota.tional veloclties of the several trituratlng rollers from one another is' iorce 01' the graphlte to be colloidally triturated.

01' course, for trlturatihg the graphlte, instead o1 mineral olls o1 low viscosity there may be employed highly vlscous materials, for example aqueous or fattymaterlals, of any desired klnd.

In the annexed drawing:

Flg. 1 is an elevational view of a palr of comventlonal grindlng rollers b a.nd c, having bearing' portlons a, illustrating the rollers In idle condition in line contact;

Flg. 2 is a view simllar to Fig. 1, but illustrates the rollers in operatlon, with materlal passlng through them and shows, to an exaggerated extent, how the rollers flex away from each other anal 1 orm a clearance d under the influen'ce 012 the wedge tormed by the material.

Fig. 3 is an elevational vlew o1 a pair ofrollers b and c .0f the character preferably used for carrylng out the present invention and wherein the rollers are spheroiclal in form. The deviation from cylindrlcal form 1s comparatlvely slight and is in the neighborhood 01 50 but lt has been exaggerated in the drawing so as to mo1e clearly illustrate the feature involved. The letter e designates the devlation from a. true cylindrlcal roller; j

F'ig. 4 ls a view taken on the llne l4 01 Fix. 3 and illustrates dlagrammatically the areas 01 the rollers that are dlsposed in surfane engagemenl; when the pressure ls appliecl thereto. These areas deflne a. trlturating zone wherein the graphite m1xture ls subjected to a, pressure of approximately 1.5 to 2.0 kilograms per square mlllimeter.

It has b een tound that specially durable suspensions 01 graphlte can be obtalned il. the graphlte ground in the ordlnary manner Is flrst mixed by stirring with blownkor thickened fatty 011s or so-called mineral oil-soluble castoroll and le1't" to swell for several 'hours anal the graphlte paste 1s then subjected in the hereinbefpre-described manner to a fine grindlng with surtaco trlturatlon under hlgh pressure. The colloldal graphlte thus produced has a. consid erably longer capaclty 1'or suspenslon in mlneral o1ls than graphlte ground on1y wlth mineral olls. It has Iurther been found thatln the presence of quantities of graphite that are only so large that the employment of a surztace trituration under hlgh pressure is rendered posslble, lt is also posslble to convert other materlals, for example colour pigments, cla.ys, soot, in a short time into an extraordinarlly flne colloidal distribution by means of the hereinbefore-descrlbed grinding under h1gh pressure. It is also advlsable Ior the Qolloldal distribution o! the.graphlte accordlng to the lnvention to employ roller mill's in which the bearlngs 01 the trlturating roller can swing freely. For the colloi dal distribution 01 the grapl 1ite therel'ore slngle-roller mills provided with trlturating bars are specially suitable in which the bearings 01 the trlturatlng roller are not fixed in the machine fra.me but are arranged therein so as to be vertically movable and in which the tzrlturating roller bears agalnst a counter trlturatlng bar which isfixed in the machlne frame und recelves the pressure 01 the trlturatlng bar which is provicled over the trlturating roller in the ordlnary way. In thlls case the bearlngs o1 the triturating roller remain entlrely wi thout pressure so that unrestrictedly high pressures can be applled. Instead 01 one trltura.ting roller there may be provided several trlturatlng rollers arranged. vertlcally one above another, the lowest roller then resting on the counter trituratlng bar.

Instand o1 the trituratlng bar and the count6r tritur ating bar pressure rollers which run in roller bearlngs 01' the llke may be employed.

1. The method of producing a colloldal graphite suspenslon whlch comprises mlxlng graphlte wlth a suspending medlum und introducing the mixture between at least two spheroldal shaped rollers anal slmultaneously Iorcing said rollers together under sufllclent pressure to deform their cylindrical walls into sur1'ace engagement to deflne a high pressure trlturatlng zone and subject said graphlte mixtufe to a pressure o1 approximately 1.5 kilograms per square millimeter, and rot'ating said rollers so as to trlturate sa1d mlxture and break the leaves 013 said graphite in dlrections substantlally normal to thelr major axes and bring the graph1te lnto colloldal Iorm, the area. o! enssement 013 sald cylindrlcal walls being sufllclently great to preclude inadvertent escape 012 said graphlte leaves trom the trlturat- Ing zone under the lnfluenc e o1 sa.ld pressure.

2. The method descrlbed in clalm 1, wherein the curvature o1 sg.id spheroidal shaped rollers 1s approxlmately 50 OTTO ALBRECHT GRAF v. MANDEIBLOH. 

